From patchwork Wed Oct 25 14:50:19 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: David Woodhouse X-Patchwork-Id: 13436353 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 0E245C07545 for ; Wed, 25 Oct 2023 14:52:01 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1344159AbjJYOv7 (ORCPT ); Wed, 25 Oct 2023 10:51:59 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:58502 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1344712AbjJYOvh (ORCPT ); Wed, 25 Oct 2023 10:51:37 -0400 Received: from desiato.infradead.org (desiato.infradead.org [IPv6:2001:8b0:10b:1:d65d:64ff:fe57:4e05]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id AC27ED50 for ; Wed, 25 Oct 2023 07:51:32 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=desiato.20200630; h=Sender:Content-Transfer-Encoding: Content-Type:MIME-Version:References:In-Reply-To:Message-Id:Date:Subject:Cc: To:From:Reply-To:Content-ID:Content-Description; bh=RxBAjsQ+mysvOozFK2bkVeJvxuxKEpOcW9P4vMvsaUw=; b=kWEwCVesu3RU1Gi+zD5e+MXOzL TI6NwMrSRoAQx1N/L//K4TlUXhKgj7PQrl+DuBhCNNSDgpxlC7tv6T7Eclwqo3JB/3jdzRkNzQ9qF quoMMtl9n21EtXIqLbI9iMJAqKE5Ob4RUIz7XAD1NO24I6Wwr+QeGorNW5GKyAU6AJbWDsEToPZSu XMKIpWSZ84bjXrvQIeIKE++0nq8nOdav05MHqaccNURQ/24YIQufkFSp5KZYBu8Or7scgLcu/6cHU UsvgICpmvIfuJWV3/+UaFP9GBwV1+sI8ZM3NKS1yiX/c3qj/QciOq9QyDey+tRL/JUEb9G4h67r4c sMq+tCFA==; Received: from [2001:8b0:10b:1::ebe] (helo=i7.infradead.org) by desiato.infradead.org with esmtpsa (Exim 4.96 #2 (Red Hat Linux)) id 1qvfDZ-00GPLx-01; Wed, 25 Oct 2023 14:50:52 +0000 Received: from dwoodhou by i7.infradead.org with local (Exim 4.96 #2 (Red Hat Linux)) id 1qvfDY-002dEF-06; Wed, 25 Oct 2023 15:50:44 +0100 From: David Woodhouse To: qemu-devel@nongnu.org Cc: Kevin Wolf , Hanna Reitz , Stefano Stabellini , Anthony Perard , Paul Durrant , =?utf-8?q?Marc-Andr=C3=A9_Lureau?= , Paolo Bonzini , "Michael S. Tsirkin" , Marcel Apfelbaum , Richard Henderson , Eduardo Habkost , Jason Wang , Marcelo Tosatti , qemu-block@nongnu.org, xen-devel@lists.xenproject.org, kvm@vger.kernel.org, Bernhard Beschow , Joel Upham Subject: [PATCH v3 05/28] hw/xen: fix XenStore watch delivery to guest Date: Wed, 25 Oct 2023 15:50:19 +0100 Message-Id: <20231025145042.627381-6-dwmw2@infradead.org> X-Mailer: git-send-email 2.40.1 In-Reply-To: <20231025145042.627381-1-dwmw2@infradead.org> References: <20231025145042.627381-1-dwmw2@infradead.org> MIME-Version: 1.0 Sender: David Woodhouse X-SRS-Rewrite: SMTP reverse-path rewritten from by desiato.infradead.org. See http://www.infradead.org/rpr.html Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org From: David Woodhouse When fire_watch_cb() found the response buffer empty, it would call deliver_watch() to generate the XS_WATCH_EVENT message in the response buffer and send an event channel notification to the guest… without actually *copying* the response buffer into the ring. So there was nothing for the guest to see. The pending response didn't actually get processed into the ring until the guest next triggered some activity from its side. Add the missing call to put_rsp(). It might have been slightly nicer to call xen_xenstore_event() here, which would *almost* have worked. Except for the fact that it calls xen_be_evtchn_pending() to check that it really does have an event pending (and clear the eventfd for next time). And under Xen it's defined that setting that fd to O_NONBLOCK isn't guaranteed to work, so the emu implementation follows suit. This fixes Xen device hot-unplug. Fixes: 0254c4d19df ("hw/xen: Add xenstore wire implementation and implementation stubs") Signed-off-by: David Woodhouse Reviewed-by: Paul Durrant --- hw/i386/kvm/xen_xenstore.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) diff --git a/hw/i386/kvm/xen_xenstore.c b/hw/i386/kvm/xen_xenstore.c index 660d0b72f9..8e716a7009 100644 --- a/hw/i386/kvm/xen_xenstore.c +++ b/hw/i386/kvm/xen_xenstore.c @@ -1357,10 +1357,12 @@ static void fire_watch_cb(void *opaque, const char *path, const char *token) } else { deliver_watch(s, path, token); /* - * If the message was queued because there was already ring activity, - * no need to wake the guest. But if not, we need to send the evtchn. + * Attempt to queue the message into the actual ring, and send + * the event channel notification if any bytes are copied. */ - xen_be_evtchn_notify(s->eh, s->be_port); + if (s->rsp_pending && put_rsp(s) > 0) { + xen_be_evtchn_notify(s->eh, s->be_port); + } } }